High-pressure integral tube coupling arrangements

ABSTRACT

Metal tubes, such as the small diameter metal tubes ( 50 ) used in hydraulic braking systems, are connected to hoses ( 23 ) also used in such systems by fittings ( 52 ) which are configured to receive radially projecting beads ( 62 ) on the metal tubes ( 50 ). Each of the fittings includes a body portion ( 51 ) with a bore therethrough and a crimping collar ( 53 ) which is unitary with the body portion ( 51 ). The body portion ( 51 ) receives an insertion end of the tube ( 50 ) therethrough, which insertion portion projects into the unitary crimping collar ( 53 ). A radially extending bead ( 62 ) on the tube is received in a recess adjacent the bore through the body portion ( 51 ). In one embodiment, the tube ( 50 ) is held in place by another bead ( 58 ) which is seated in another recess at the opposite end of the bore.

FIELD OF THE INVENTION

[0001] The present invention relates to high-pressure integral tubecoupling arrangements. More particularly, the present invention relatesto such arrangements for coupling flexible hoses, such as a reinforcedrubber hoses to metal tubes for use in systems such as vehicle brake andclutch systems.

BACKGROUND OF THE INVENTION

[0002] In discussing the automotive industry, the Background of U.S.Pat. No. 5,037,142 states: “a wide variety of connector devices havebeen utilized to connect tubes to hoses for conducting fluidtherethrough or transmitting a hydraulic force through a column of oilcontained therein. in many cases, specialized couplings are requiredwhich not only hydraulically connect adjacent tubes or pipes, hoses andother conduits in a fluid-tight manner, but also provide effectivesupport while allowing relative movement of components and providingprotection in relatively harsh environments.”

[0003] Current methods for joining hoses to metal tubes stillsubstantially rely on threaded couplings in which an externally threadedhollow nut is threaded into a internally threaded fitting to hold aflared tube tightly within the fitting. Since both the nut and thefitting must be machined, they are relatively expensive. In addition,making the connection is time consuming and labor intensive because itis not conveniently adaptable to automation. Moreover, quality controlis difficult because there is the possibility of threaded componentsbeing joined without proper alignment so that threads are stripped,resulting in joints that leak and are subject to failure when operatedat high pressures over long time periods of time in adverseenvironments. In view of these difficulties, there have been attempts toform couplings which do not require threaded components. Brazing a tubeonto a hose fitting is one approach. Since these couplings arefrequently exposed when used with brake systems, clutches and hoses,they are subject to environmental degradation because of moisture, roadsalt, wide temperature fluctuations and mechanical impacts andvibrations, all of which combine to accelerate corrosion. In order toprotect brazed joints from corrosion, it is necessary to plate theassemblies which is in and of itself a relatively expensive undertaking.Moreover, these assemblies frequently require parts which have multipleelements each of which has the potential to provide a leak path and eachof which must be handled and stored.

[0004] The technology of coupling hoses and tubes is now generally goingto “quick-connect” type couplings in which all that is required toachieve a fluid tight connection is for two components being joined tobe axially pushed toward one another, so that there is no need to rotatecomponents of a coupling, one with respect to the other. When couplingmetal tubes to rubber hoses, it is the practice to crimp the rubber hosewithin the coupling which is a rapid, reliable process requiring only asingle metal-deforming step once the hose is inserted into the coupling.In order to further simplify assembly so as to reduce cost, it isdesirable to simplify connecting the tube to a crimpable fitting.

SUMMARY OF THE INVENTION

[0005] In view of the aforementioned considerations, it is a feature ofthe present invention to provide new and improved tube-to-hose couplingswhich are reliable, inexpensive and yet require manufacturing stepswhich are minimal and do not introduce difficulties of their own.

[0006] In view of this feature and other features, the present inventionis directed to a coupling arrangement for connecting a tube to a hosewherein the tube has a main portion and an insertion portion, theinsertion portion being inserted through the fitting into the hose. Thetube further has at least a first outwardly extending radial projectionwhich cooperates with the fitting, the insertion portion of the tubeextending beyond the radial projection to the terminus of the tube. Thefitting has a first portion with a bore for receiving the tubetherethrough and a second portion extending axially from the firstportion for receiving the hose therein, with an interior surface on thefirst portion facing the second portion. The tube is disposed in thebore of the fitting with the outwardly extending projection abutting theinterior surface on the first portion and the insertion portionextending into the second portion of the tube for insertion into thehose.

[0007] In a further aspect, the fitting includes a second abutmentsurface thereon facing away from the second portion for opposing axialmovement of the tube toward the second portion of the fitting, and in astill further aspect, the portion of the tube engaged by the secondabutment surface is on the first projection.

[0008] In a further aspect, the second abutment surface is on a portionof the fitting which is radially and axially deformed into abutment withthe second abutment surface.

[0009] In still a further aspect, the second axially extending abutmentis at a radially extending end of the fitting.

[0010] In a further aspect, the second portion of the fitting is acrimping collar for radially engaging the hose while the insertionportion of the tube is within the hose.

[0011] In still a further aspect of the invention, the main portion ofthe tube is covered with a layer of deformable protective material withthe insertion portion and radially extending radial protection beinguncoated. In accordance with this aspect of the invention, there is ametal-to-metal seal between the fitting and the uncoated radialprojection. On the other hand, the deformable protective material may bepressed into the fitting to provide a sealing area.

BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Various other features and attendant advantages of the presentinvention will be more fully appreciated as the same becomes betterunderstood when considered in conjunction with the accompanyingdrawings, in which like reference characters designate the same orsimilar parts throughout the several views, and wherein:

[0013]FIG. 1 is a perspective view of a prior art arrangement forjoining a metal tube to a flexible hose;

[0014]FIG. 2 is a side view, mostly in elevation, showing a firstembodiment of a prior art threaded coupling used to join a tube to ahose;

[0015]FIG. 3 is a side view, mostly in elevation, showing a secondembodiment of a prior art threaded coupling used to join a metal tube toa hose;

[0016]FIG. 4 is a side elevation of a prior art brazed joint used tocouple a metal tube to a flexible hose;

[0017]FIG. 5 is a side view, mostly in elevation, showing a firstembodiment of a coupling in accordance with the present inventionutilized to couple metal tube to a flexible hose;

[0018] FIGS. 6A-6D are side views, mostly in elevation, illustrating thefabrication and assembly of the coupling of FIG. 5;

[0019]FIG. 7 is a side elevation showing the tube of the presentinvention, but for clarity illustrated without the fitting;.

[0020]FIG. 8 is a side elevation of a fitting shown in FIGS. 5, 6B and6D showing an embodiment of the fitting with pockets for receiving beadsformed on the tube;

[0021]FIG. 9 is a side elevation of a second embodiment of the fittingof FIGS. 5, 6B and 6D having no pockets for receiving beads on the tube;

[0022]FIG. 10 is a side elevation showing a third embodiment of theinvention;

[0023]FIG. 11 is a side elevation of a fourth embodiment of theinvention; and

[0024] FIGS. 12A-D are side elevation views showing a preferred assemblytechnique for embodiment of the invention illustrated in FIG. 11.

DETAILED DESCRIPTION

[0025] Prior Art Arrangements: FIGS. 1-4

[0026] Referring now to FIG. 1, there is shown a prior art couplingarrangements 19 for connecting relatively small diameter tubes 20 suchas brake tubes to fittings 21 by threaded insert-type connections 22.The fittings 21 are crimped to a hose 23 which carries relatively highpressure hydraulic fluid. In FIG. 1, a part of a truck chassis or frame24 retains the coupling 19 thereon with a bracket 25 to hold thecoupling rigid with respect to the frame. The hose 23 is relativelyflexible and may be retained to other portions of the chassis by clampswhile the tubes 20 may also be retained to the chassis 24 by clamps 25.One of the tubes 20 is attached to a hydraulically driven device such asa brake caliper 28 in a disk brake 29. The present invention replacesthe couplings 19 with a more reliable and more economical couplingarrangements. While a disk brake 29 is shown in FIG. 1, the inventionhas other uses for other types of hydraulic connections such asconnections for clutches, and any other arrangement in which a flexiblehose is connected to a rigid tube.

[0027] Referring now to FIGS. 2 and 3 which show in more detail theprior art coupling 19 of FIG. 1, it is seen that the threaded nut 22 isreceived in a threaded recess 31 of the fitting 21 while the hose 23 iscrimped to the fitting via a crimping collar 32. In the arrangement ofFIG. 2, the tube 20 has a flared end 33 and the fitting 21 has aninverted or convex seat 34. In the embodiment of FIG. 3, the fitting 21′has a concave seat 34′ which receives a bubble end 33′ of the tube 20′.The externally threaded nut 22′ then threads into the threaded bore 31′in the same way that the threaded nut 22 threads into the threaded bore31 of FIG. 2. In practice, the arrangements of FIGS. 2 and 3 tend tohave multiple components.

[0028] Referring now to FIG. 4, in an attempt to avoid the expense andminimize the difficulties of a coupling 19, such as the coupling ofFIGS. 2 and 3, wherein an externally threaded nut 22, 22′ must bethreaded into a threaded bore 31, 31′, the tube 20″ of FIG. 4 ispress-fitted into a smooth recess 31″ of a fitting 21″ and copper brazedat juncture 36. The fitting 21″ is then plated, which requires platingof an assembly that has the relatively long portion of the tube 20″attached to the fitting 21″. In practice, the arrangement of FIG. 4 alsotends to use an insertion tube 37, which results in more part-to-partjunctures that increase the number of potential leak paths.

[0029] Embodiments of the Invention: FIGS. 5-12

[0030] In order to improve upon the couplings illustrated in FIGS. 1-4as well as other couplings, the present invention eliminates a need tophysically join the components of the tube-to-hose couplings by hand atassembly plants, as well as reducing leak paths, component costs andpart number counts. Moreover, as opposed to brazed tube designs, such asthat of FIG. 4, tolerance control is increased, as is routing control.

[0031] Referring now to the first embodiment of the present inventionillustrated in FIGS. 5-9, a high pressure integral tube coupling 40enables a direct connection between a metal tube 50 and a flexible hose23 (see FIG. 1), such as a high pressure resistant rubber hose, withouta need for rotating threaded coupling components or brazing, thuseliminating parts or steps while retaining their function. As is seen inFIG. 5, the metal tube 50 is positioned within a body portion 51 of afitting 52 to which the hose 23 of FIG. 1 is subsequently coupled bydeforming a crimping collar 53 therearound so that the hose is axiallyretained within the fitting 52 and is radially sealed against an endportion 54 of the tube. The tube 50 corresponds to the tubes 20 shown inthe prior art arrangements of FIGS. 1-4 and has an internal diameter ofabout 0.1250 inch, which internal diameter could range from about 0.125to about 0.145 inch.

[0032] In order to retain the tube 50 in the fitting 52, a back bead 56is preferably seated within an annular bead pocket 58 formed in a backend 59 of the fitting 52 while a front bead 60 is preferably seated in apocket 62 formed in front end 63 of the fitting located just before thecrimping collar 53. A smooth bore 66 extends completely through thefitting 52 into a cylindrical space 68 defined by the crimping collar53. While the pockets 58 and 62 are preferable, it is within the scopeof this disclosure to form the coupling without the pockets by crimpingthe tube 50 directly against the radial end surfaces of the fitting (SeeFIG. 9).

[0033] The diameter d₁ of the smooth bore 66 is slightly greater thanthe diameter d₁ of the tube 50 so that the tube slides through thesmooth bore. While the diameter d₁ is slightly larger than the diameterof d₂, it need only be large enough so that the d₂ will slide readilytherethrough. There could, however, be a slight press fit of the tube 50within the bore 66.

[0034] The end 54 of the tube 50 has a reduced diameter portion 67 of adiameter d₃ which is slidably receivable within the bore 70 of the hose23 and is of a length substantially equal to that of the crimping collar53. Consequently, the bore 70 of the hose 23 is supported during thecrimping step which deforms the material 72 of the hose.

[0035] Referring now to FIGS. 6A-6D which illustrate the methodfabricating and assembling the coupling 40, it is seen that the metaltube 50 has its end portion 54 drawn to have the reduced diameter d₃which is less than the diameter d₂ of the tube 50. As is seen in FIG.6B, the back bead 56 is formed by an applied force which pushes aportion 76 of the tube 50 back, thus forming a beaded area in proximitywith line 78.

[0036] As is seen in FIG. 6C, the thus deformed tube 50 is insertedthrough the smooth bore 66 of the fitting 52 so that the back bead 56fits into the annular bead pocket 58 at the back end 59 of the body 51of the fitting. The annular bead pocket 58 is formed in or machined inthe back end 59 of the fitting and has a diameter substantially greaterthan the diameter d₂ of the smooth bore 66. It is to be kept in mindthat the bead pocket 58 is a desirable but optional feature. Referringnow to FIG. 6D in combination with FIG. 6C, the front bead 60 is thenformed by using an applied force to the tube 50 rearwardly so that aportion 80 of the tube 50 deforms into the front bead 60 which seatswithin the annular front bead pocket 62 at the front end 64 of the body51 of fitting 52. The structure of the tube 50 in the absence of thefitting 52 is shown in FIG. 7, while the structure of the fitting absentthe tube is shown in FIG. 8.

[0037] In the first embodiment of the invention, it is seen that thecoupling 40 is accomplished by two axial deformations of the tube 50,one prior to inserting the tube 50 into the fitting 52 and the othersubsequent to the insertion. The final step is to radially crimp thecrimping collar 53 which is a conventional one-step procedure. If thearrangement is to be used with the brake line of FIG. 1, the fitting 52with the tube 50 connected thereto may be first inserted into an openingin the bracket 25 and a sliding clip slid into the annular groove 87 inthe fitting 52. The hose 23 is then inserted in the space 68 in thecrimping collar 53 and the crimping collar crimped about the hose. Byhaving a press fitting between the tube 50 and the fitting 52, rotationof the fitting relative to the tube is eliminated while maintaining afluid tight seal.

[0038] Preferably, the metal tube 50 is made of steel and is pre-coatedby SAE-J527 Standards, sliding fit. Other materials which may be usedare copper, nickel, NYLON® (polyamide) or polyvinyl fluoride. Ifrelatively thick plastic coatings such as NYLON® are used, the coatingpreferably terminates before the first bead 56; however, as is seen inthe third embodiment of FIGS. 10 and 11, can continue to bead 60. Thebarbed or stem structure beyond the beads 56 and 60 has a controlledinside diameter as well as a controlled outside diameter which permitsthe assembly to pass the Federal Motor Vehicle Safety Standards forminimum fluid passage diameter. Moreover, the barb or stem structure canbe produced either with or without annular grooves to increase tensileintegrity of the coupling. Since the end 54 of the tube is receiveddirectly within the bore 70 of the hose 23, potential leak paths whichoccur with additional elements, such as those in prior art threadedconnections and brazed tubular supports, are eliminated.

[0039] Referring now to FIG. 9, there is shown a second embodiment ofthe invention, wherein the bead pockets 58 and 62 are deleted from thefitting 52′ so that beads 56′ and 60′ press directly against theradially extending back and front end surfaces 80 and 82, respectivelyof the fitting 52′. Friction between the end surface 80 and back bead 56and between the front end surface 82 and the front bead 60 preventsrotation of the tube 50 within the fitting. In addition, there is aslight friction fit between the tube 50 and the bore 66′ which providesa fluid seal.

[0040] Referring now to FIG. 10, there is shown a third embodiment ofthe invention wherein a tube 90 is inserted into a fitting 92 having acrimping collar 93. The tube 90 has a necked down portion 94 joinedthereto by a frusto-conical section or tapered 95. The frusto-conicalsection 95 joins an intermediate section 96 just in front of a bead 97.The fitting 92 has a smooth bore 100 that has an abutment surface 101defined by an annular shoulder 102 therein that is disposed within in anannular recess 104. As with the embodiment of FIGS. 5-9, the tube 90 isshoved into the fitting 92 (as shown in FIG. 6C) until the bead 97 abutsthe shoulder 102 of the abutment surface 101. An annular portion 106 ofthe wall of the recess 104 is then deformed by staking the portion 106against the bead 97 to retain the tube 90 within the bore 100 of thefitting 92. Thereafter, a portion 110 of a second annular recess 112within the fitting proximate the crimping collar 93 is deformed againstthe tapered section 95 of the tube 90 to provide a tapered portion 113of the bore 100 against which the tapered portion of the tube seats.This seals the tube 90 within the fitting 92 at substantially threelocations, whereafter the hose 23 is secured within the fitting 92 bydeforming the crimping collar 93. The arrangement of the secondembodiment of the invention shown in FIG. 10 is used substantially asthe arrangement of the first embodiment shown in FIGS. 5-9. As with theembodiments of FIGS. 5-8 and 9, the embodiment of FIG. 10 is used insituations such as that of FIG. 1 where a flexible hose 23 connects asource of hydraulic fluid to a tube 20, which tube retains fluid whichoperates a hydraulic device, such as the calipers of a brake, or aclutch, or any other device requiring high pressure hydraulic fluiddelivered via a flexible hose.

[0041] Referring now to FIGS. 11 and 12A-D, there is shown a fourthembodiment of the invention wherein a metal tube 200 is coupled to thehose 23 by a fitting 202 to form a coupling 203. The metal tube 200 hasa drawn down portion 204 which has a relatively small outside diameterd₁ which is less than the outside diameter d₂ of a main portion 205 ofthe tube. In addition, the tube 200 has an annular bead 206 having afirst axially facing surface 208 and a second axially facing surface210. Tube 200 is received through a smooth bore 212 in a body portion213 of the fitting 202 and, if the metal tube does not have a plasticcoating, may have an interference fit. Tube 200 is retained within thefitting 202 by abutment between the first surface 208 of the bead 206with a shoulder 216 adjacent the bore 212 and by a swaged, staked orannular portion 218 of the fitting 202 that forms a second abutmentwhich engages the surface 210 of the bead. The fitting 202 and tube 200are therefore prevented from any axial or rotational movement, one withrespect to the other while also being provided with metal-to-metal fluidseals 219 and 216 which prevent entry of moisture and corrosive agentsthat might degrade the interior of the coupling.

[0042] Preferably, the main portion 205 of the metal tube 200 is coatedor covered with a layer 220 of a plastic material such as, for example,a polyamide, i.e., NYLON®, which layer of plastic material terminatesbefore or at the bead 206 leaving the bead uncoated for themetal-to-metal seal 219 with the fitting as well as leaving the smalldiameter portion 204 uncoated for ready receipt in the bore of the hose23. Examples of other plastic materials which may be used arepolyvinylfluoride or polypropylene.

[0043] A preferred example of a tube configuration for the tube 200comprises a base tube of SAE 1008/1010 mild steel with a layer of copperplating over which is a 10-15 μm 95% zinc/5% aluminum hot dip coating.The layer of plastic material 220 is preferably a layer of polyamideover a binder layer which is on average about 3.5 μm thick.

[0044] Referring now to FIGS. 12A-12D, preferred steps in assembling thecoupling 203 are shown in sequence. As is seen in FIG. 12A, tube 200 isprovided. Tube 200 is drawn to provide the small diameter portion 204and to form frusto-conical portion 222 which joins the small diameterportion 201 to the remainder of the tube 200. As is seen in FIG. 12B,the tube is deformed by pressing axially against the tube so that itbulges outwardly to form the bubble 206 generally in the location of thefrusto-conical portion 222. If the entire tube 200 has previously beencoated with a plastic layer 220, the plastic layer is stripped from theinsertion portion 204 and the bead 206 prior to drawing.

[0045] There are a number of methods to remove a portion of the plasticlayer 220 from a portion of the tube 200. These methods include applyingmechanical cutting tools, abrasive wheels or brushes or using laserablation, chemical solvents or water jet ablation. The tube 200 may beaxially moved and rotated as the plastic and other non-metallicmaterials are stripped therefrom preferably prior to drawing orotherwise deforming the tube 200.

[0046] Referring now to FIG. 12C, the fitting 202 is slid along thelength of the tube 200 from its opposite end or, in the alternative, thetube is simply inserted into the bore 212 until the surface 208 on thebead 206 is abutted by the shoulder 216 that is adjacent the end of thebore. Preferably, the fit between the tube 200 and the bore 212 is asliding fit with the plastic layer 220 sliding within the bore. The fitbetween the tube 200 and bore may be sufficiently tight to form a fluidtight seal. As is seen in FIG. 16D, the annular portion 218 of the wideportion of the bore 212 is then swaged or staked against the second face210 of the bead 206 in order to form the coupling 203 which firmlyretains the tube 200 within the fitting 202 and forms themetal-to-metal, fluid tight seal 219 therewith.

[0047] After the coupling 203 is formed, the hose 23 (FIG. 11) isinserted into a hollow portion 230 of the fitting 202 which forms acrimping collar that is unitary with the body portion 213 of thefitting. The crimping collar 230 is then deformed radially inwardly toretain the hose 23 permanently and non-rotatably in communication withthe tube 200.

[0048] By utilizing the arrangement of the present invention, tubes areretained within fittings, such as fittings for joining the tubes tohoses, utilizing mechanical steps which involve neither rotating thetube with respect to the fitting, brazing the tube to the fitting orusing a retaining unit.

[0049] From the foregoing description, one skilled in the art can easilyascertain the essential characteristics of this invention, and withoutdeparting from the spirit and scope thereof, can make various changesand modification of the invention to adapt it to various usages andconditions.

What is claimed is:
 1. A coupling for connecting a tube to a hosecomprising: a tube having a main portion and an insertion portion; atleast one outwardly extending radial projection on the tube, with theinsertion portion of the tube extending beyond the radial projection; afitting having a body portion with a bore for receiving the tubetherethrough and a hollow portion extending from the first portion forreceiving the hose therein; an inside radial surface on the body portionfacing toward the hollow portion; and the tube being disposed in thebore of the body portion with the outwardly extending radial projectionabutting the inside radial surface on the body portion and the insertionportion extending into the hollow portion of the fitting for receipt inthe hose.
 2. The coupling of claim 1, wherein the body portion of thefitting includes an abutment surface thereon facing away from the hollowportion and engaging a portion of the tube.
 3. The coupling of claim 2,wherein the portion of the tube engaged by the abutment surface is onsaid one outwardly extending radial projection.
 4. The coupling of claim3, wherein the abutment surface is on a portion of the fitting which isradially and axially deformed into abutment with said one outwardlyextending radial fitting.
 5. The coupling of claim 2, wherein there is asecond outwardly extending radial projection on the tube, spaced axiallyfrom said one outwardly extending radial projection, and wherein theabutment surface on the fitting engages the second outwardly extendingradial projection on the tube.
 6. The coupling of claim 5, wherein thesecond axially extending abutment is at a radially extending end of thefitting.
 7. The coupling of claim 6, wherein the insertion portion has adiameter less than that of the main portion of the tube.
 8. The couplingof claim 7, wherein the hollow portion of the fitting is a crimpingcollar for radially engaging the hose with the insertion portion of thetube within the hose.
 9. The coupling of claim 1, wherein the insideradial surface facing the hollow portion is a flat surface engaged bythe radial projection and wherein there is an outside radial surfacefacing away from the hollow portion and defining another flat surfacewhich is engaged by another radial projection on the tube.
 10. Acoupling for connecting a tube to a hose comprising: a metal tube havinga main portion and an insertion portion, the insertion portion having anouter diameter corresponding to the inner diameter of the hose forinsertion therein and a controlled inner diameter; a radial projectionon the metal tube adjacent the insertion portion, the radial projectionhaving oppositely facing surfaces; a layer of plastic material coveringthe main portion of the tube and terminating at the radial projection,the radial projection being free of plastic material; a fitting having abore therein slidably receiving the main portion of the metal tube, thefitting including an abutment surface extending radially of the bore andincluding an annular recess in which the radial projection on the tubeseats, the abutment surface being within a crimping collar that isunitary with the fitting; and an annular deformed portion adjacent theannular recess, which annular deformed portion is deformed into abutmentwith the radial projection to form a metal-to-metal fluid tight sealwhich also fixes the metal tube to the fitting.
 11. The coupling ofclaim 10, wherein the metal tube has an outer diameter which is largerthan the outer diameter of the insertion portion.
 12. The coupling ofclaim 11, wherein the fitting has a unitary hollow portion which extendsbeyond the abutment surface and surrounds the insertion portion of themetal tube wherein the hollow portion receives the hose.
 13. Thecoupling of claim 11, wherein the unitary hollow portion receives thehose therein and wherein the hollow portion is crimped against the hosewith the insertion portion of the tube received within the hose.
 14. Thecoupling arrangement of claim 13, wherein the hollow portion is coaxialwith both the main portion and insertion portion of the metal tube. 15.The coupling of claim 13, wherein the tube, hose and fitting arecomponents of a hydraulic or other automotive fluids as required and areadapted to be filled with hydraulic fluid.
 16. The coupling of claim 10,wherein the layer of plastic material is in a sealing relationship withthe bore of the fitting.
 17. The coupling arrangement of claim 16,wherein the layer of plastic material is selected from the groupconsisting of polyamide, polyvinylfluoride and polypropylene.
 18. Thecoupling arrangement of claim 12, wherein the metal tube has a taperedsection joining the insertion portion to the main portion and whereinthe bore has a corresponding tapered portion against which the taperedportion of the metal tube seats.
 19. The coupling arrangement of claim18, wherein the abutment surface of the fitting is disposed adjacent themetal tube within the fitting when the annular deformed portion isdeformed against the radial projection and the main portion of the tubeextends away from the fitting and wherein the tapered portion of thefitting is positioned adjacent a crimping collar that is unitary withthe fitting so that the insertion portion of the metal tube extendswithin the crimping collar for receiving and clamping the hose thereinwith the insertion portion in the hose.